1. Field of the Invention
The present invention relates generally to foamed polyurea elastomers and, more particularly, to rigid, closed cell polyurea elastomer foams prepared from, among other things, primary aliphatic amines. 2. Description of Background Art
In general, polyurea foams have been used in molded foam applications, such as in the manufacture of automobile interiors (seating, etc.), as well as in slabstock foams, which are oftentimes used as carpet underlay or in furniture applications. Polyurea foams have also demonstrated utility in a wide variety of other padding or cushioning applications.
The polyurea foams of the present invention are specifically rigid, closed-cell foams which are most typically employed as insulation, simulated wood parts, such as speaker cabinets, picture frames, doors and the like, packaging foams and shock absorbing foams, to name a few.
As is recognized in Priester, R. D. et al., High Resiliency Polyurea Foam --An Improved Flexible Foam Matrix, a paper distributed at the 32nd ANNUAL POLYURETHANE TECHNICAL/MARKETING CONFERENCE, Oct. 1--4 (1989), it is quite difficult to prepare polyurea foams using primary aliphatic amines due to their rapid rate of reactivity with isocyanates.
Surprisingly, the rigid, closed cell polyurea foams of the present invention are prepared using, among other things, primary aliphatic amines.
U.S. Pat. No. 4,910,231 describes substantially water blown flexible polyurethane foams which are prepared by reacting methylene diphenyl isocyanates with water and one or more isocyanate-reactive compounds selected from polyols and polyamines. In column 2, lines 62-66, and in other parts of the patent, patentees disclose that halocarbon blowing agents are used in addition to water. Thus, this patent does not describe water as the sole blowing agent.
U.S. Pat. No. 4,904,705 describes polyurea foams made from N-(polyoxyalkyl)-N-(alkyl)amines, by reacting said amines with isocyanates and by subsequently employing a small amount of blowing agent in the reaction mixture. This patent teaches away from using primary amines to prepare polyurea foams, due to their extremely high reactivity.
U.S. Pat. No. 4,797,430 describes amine-modified polyurethane (urea) foams and a process for their production. More specifically, the foams are prepared by reacting a relatively high molecular weight isocyanate-reactive compound with a polyisocyanate and an amine. Blowing agents are used to produce the resulting foam, one of which can include water.
U.S. Pat. No. 4,748,192 describes aliphatic polyurethane sprayable coating compositions and a method for their preparation. Specifically, a caprolactone polyol is reacted with an aliphatic isocyanate in the presence of a metallo catalyst and an amine curing agent. Patentee generally describes that his coating composition can be foamed by employing a blowing agent, such as water.
U.S. Pat. No. 4,732,919 describes a reaction injected molded elastomer made by reacting a high molecular weight polyol or polyoxyalkylene polyamine, a chain extender and a quasi-prepolymer of a polyoxyalkylene polyamine and an aromatic isocyanate. While the patent contains no description of a foam, it does describe blowing agents as an additional ingredient in column 5, line 28.
U.S. Pat. No. 4,705,814 describes a reaction product of a polyoxyalkylene polyamine and an isocyanate, wherein the polyoxyalkylene polyamine is present in less than the stoichiometric amount. As in the case of U.S. Pat. No. 4,732,919, this patent does not describe foams but describes the use of blowing agents as additional ingredients.
U.S. Pat. No. 4,469,657 describes a RIM elastomer which comprises the reaction product of a high molecular weight polyhydric polyether, a low molecular weight active hydrogen containing a compound of at least two functionality and a polyisocyanate in the presence of a single tin catalyst or a mixture of tin catalysts wherein two components are reacted together. All of the tin catalyst is placed with the isocyanate component prior to reaction. This patent does not relate to foams but, like some of those patents discussed above, describes employing blowing agents as other ingredients. Blowing agents are described as low-boiling hydrocarbons, carbon dioxide and nitrogen; water is not mentioned.
European Patent Application No. 0 286 005 describes flexible, open cell polyurea foams prepared by reacting a high equivalent weight amine terminated compound, a blowing agent, a crosslinker and a polyisocyanate. Thus, this publication does not relate to the rigid, closed cell foams of the present invention.